Centrifugally operated mercury switch



Patented Sept. 28, 1943 UNITED STATES PATENT OFFICE CENTRIFUGALLY OPERATED MERCURY SWITCH n Joseph H. Staley, Columbus, Ind. Application December 16, 1939, Serial No. 309,524

8 Claims.

This invention relates yto a mercury switch of the type having a quantity of mercury owable between two parts of a metallic envelope. The invention herein relates specifically to a switch structure particularly adapted for centrifugal operation `v'lherein the closing and opening of an electrical circuit is produced by the change in shape of a globule of mercury under centrifugal action rather than by a flow bodily of the entire mass of mercury from one part of the envelope to another.

One particular advantage of the present invention is `the high degree of sensitivity obtained. Another important advantage is that there is but a small number of intervening revolutions between the closing and opening of the circuit.

These and other important advantages of the invention will become apparent to those versed in the art in the following description of one particular form of the invention as illustrated in the accompanying drawing, in which Fig. 1 is a central transverse section through a structure to which the invention is applied;

Fig. 2, a section on the line 22 in Fig. 1;

Fig. 3, a longitudinal diametrical section through a switch embodying the invention; and

Fig. 4, a transverse section on the line 4`4 in Fig. 3

Like characters of reference indicate like parts throughout the several views in the drawing.

Referring rst Vto Fig. 3 of the drawing, an envelope is formed out of any suitable material, such as iron, to consist essentially of a tubular body I l) integrally closed at at the other and having an exterior portion adjacent the open end reduced in diameter preferably from that of the remainder of the tube to receive thereover an insulating sleeve II to be telescopically engaged by a cap I2 likewise made out of iron. The sleeve II is made out of any suitable resilient insulating material and is compressibly engaged between the body I0 and the cap I2 with sufficient frictional engagement so as to rmly retain the cap I2 in position thereover against considerable internal pressure. the form herein shown, the sleeve I I is in two lengths separated by an intervening elastic seal I3 as shown and described in. my Patent No. 2,045,003, issued June 23, 1936.

In the outer end of the sleeve II which is made to extend beyond the open end of the body I0 is frictionally engaged a ceramic annulus I4 hereinafter termed a breaker. This breaker I4 is iirmly gripped by the resilient sleeve II by the cap I2 thereover so that the breaker is fixed in to fill in that part of longitudinal position in respect to the various elements. The breaker I4 may have a slight clearance left between it and the end of the body I0, as indicated in Fig. 3, or it may be abutted thereagainst as indicated in Fig. 1. Preferably the clearance is provided in order to thoroughly insulate the breaker I4 against externally produced shocks such as would be set up by dropping the switch or the like. The breaker I4 is, in any event, of insulating material of a character resisting deterioration in the presence of electric arcs that may be produced upon the making and breaking of a circuit 'thereoveig and is particularly provided to protect the resilient liber sealing sleeve II. l

To the cap I2 is secured in any suitable manner an axially positioned electrode I5 in the nature of a rod, to have a length carrying it well within the body I0 te terminate near the closed end thereof. This rod I5 is preferably made out of iron and may be secured by welding it to the inside of the cap I2 or by boring a hole through the cap I2, as suggested in Fig. 3, and then Weldlng to insure not only a xed position but also a gas tight seal therearound through the cap. I'he diameter of this rod I5 is such that it lls the major proportion of the cross-sectional area of the central bore through the breaker I4 thereby leaving an annular opening therearound of limited area, as indicated in Fig. 4.

A quantity of mercury I6 is placed within the body IO before the cap I 2 is forced thereover in the sealing operation and as, is the usual practice, the atmospheric gases are evaporated and replaced by some gas such as hydrogen. The quantity of mercury I 6 employed is just suicient the cap I2 beyond the breaker I4, the annular chamber in the breaker about the rod I5 and to come in co-ntact for a short distance with the open end of the body I 0 when the cap I2 is turned downwardly as indicated in both Figs. 1 and 3. The area of contact of the mercury I6 with the body IG above the breaker I4 is made to be sufficient to carry the desired amount of current for which the switch is rated without causing undue heating arising from resist-ance.

This type of switch is intended to be operated by revolving the switch bodily around an axis of revolution to have the axis of the switch fixed permanently parallel with that axis of revolution.

One particular mechanism for so mounting and whirling the switch is indicated in Figs. 1 and 2 wherein the switch structure above described carries terminal bands II and I8 about the respective body and cap ends to have the ends of these bands secured one over the other to an insulating block I9 which in turn is sef cured to a metallic post 20. This metallic post bear against the respective rings 26 and 21 in order to provide circuit connections therewith and hence with the Abody and cap ends oi the switch.

The brushes 28 and 29 are, of course, held inV xed positions relative to the turning of the post 23.

Depending upon the size and proportions of the Switch parts, the mercury IB ltherein will remain in Contact with both the body l and the rod l up and through predetermined speeds of lrevolution of the switch. Above such speeds, the mercury iii will tend to overcome its skin eiect or cohesion normally tending to hold it in a spherical shape and flatten out against that side ofthe switch furthest removed from the axis of revolution to assume some such shape as suggested in Fig. 3 where there will be a thin sheet of mercury above the breaker ld pressed by centrifugal action against the body I@ withpossicly a lesser amount down below the breaker iii in the well thereunder inthe cap l2, the original body of mercury having separated into these two bodies with the line of division occurring substantially at the stop 'of the breaker lf3 where the arc would be entirely cutoirby the mercury above and below that divisional zone.- Primarily the circuit interruption occurs between the mercury and the rod l5 above the breaker ill. Thus in this condition, the mercury has so positioned itself underthe effect of centrifugal action as to have interrupted the circuit between the body l0 and the rod I5 by this ilattening action. The body l0 does not tilt but remains xed in parallel alignment as above indicated with the axis of revolution.

This circuit interruption may be employed,

y of course,in a conceivably wide range of methods of speed control, the particular methods not entering per Se into the present invention. As soon Ias the speed has dropped following the circuit interruption sufciently to permit the gravitational effect and inherent cohesion to operits unitary condition to reestablish the circuit between the body lil through the breaker lll with the cap I2. It is to be noted that any arcs produced upon either the making or breaking of the circuit must occur immediately adjacent or withinthe breaker l to be essentially surrounded initially by masses of mercury.

The switch'above described functions admirably in combination with a tilting switch 3b mounted to operate in the manner indicated and shown in my pending kapplication for patent, Serial No. 143,087, particularly in respect to Fig. 3 thereof. This switch 3Q is pivotally mounted by the pin 3l on the insulating block 32 fixed to the base 2| so that its upper end may swing outwardly from the axis of revolution under the eiiect oi centrifugal action sub-ject to lthe pull ate on the mercury, the mercury will re-assume of the restraining spring 33 which, in the present form, is shown as being interconnected between the terminal clip 34 about the body end of the switch 3i) and an ear on the upper end of the post 20.

The switch 3B, in the present form, is shown as having a cap 35 telescoping over an insulating sleeve 36 to carry it compressibly against the exterior part adjacent the open end of the body part of the switch 30 and a ceramic breaker 3'! is positioned between the end oi the body and the cap as indicated to leave an opening through the breaker 3l substantially equal in diameter -lto the interior diameter of the body of the switch.

A mass of mercury 33 is carried withinvthe switch and this mass flows up and down the wall of the switch as it is inclined from and returns toward the vertical position as the speed may vary in whirling the switch around the axis of rotation. The terminals from this switch 3! likewise lead to the contacting rings 2S and 2l in order to provide connections for the controlling circuit.

In reference tothe use of the invention, a wide range of controls may be effected. For example, one switch may be connected into a circuit to provide a closed circuit at certain speeds and the other switch will be so connected as to open that circuit upon a predetermined speed being reached thereabove. The particular advantage in the use of the two types of switches is that the one centrifugal control device may be used in not only starting an electric device, such as a motor, but also in controlling its speed within predetermined limits, one switch controlling apart of the range of speeds and the other switch controlling another range. Those versed in the art will readily appreciate the further advantages of the use of this particular combination.

While the invention has herein been shown in the one particular form, it is obvious that structural variations therefrom may be employed without departing from the spirit of the invention and it is, therefore, desired that the invention not be limited to that precise form beyond the limitations as may be imposed by the following claims.

The invention claimed is:

l. A mercury tube switch for centrifugal operation comprising a constant diameter tubular metallic envelope; a rod-like electrode insulatedly supported by the envelope and extending axially into and along substantially the entire length of the envelope; a ceramic breaker formed as an annulus to surround said electrode; said breaker being located at one end of the envelope; means for revolving the switch; means mounting the switch with its axis iixed substantially parallel to and eccentrically oi the axis of revolution of said revolving means; and a limited quantity oi mercury in said envelope; whereby said mercury may tend to form a globular mass at any position along said envelope beyond said breaker and normally be in contact with said electrode to complete a circuit between the electrode and the envelope, and upon revolution of the switch bodily with axis parallel to the axis of revolution, said mass will flattenv and withdraw from said eiectrode Contact.

2. A mercury tube switch for centrifugal operation comprising a constant diameter tubular metallic envelope; a rod-like electrode insulatedly supported by the envelope and extending axially into and along substantially the entire length of the envelope; a ceramic breaker formed as an annulus to surround said electrode; said breaker being located at one end of the envelope; means for revolving the switch; means mounting the switch `with its axis fixed substantially parallel to and eccentrically of the axis of revolution of said revolving means; and a limited quantity oi mercury in said envelope; whereby said mercury may tend to form a globular mass at any position along said envelope beyond said breaker and normally be in contact with said electrode to complete a circuit between the electrode and the envelope, and upon revolution of the switch bodend of the envelope and insulated therefrom; and said electrode being xed to said closure.

3. A mercury tube switch for centrifugal operation comprising a tubular metallic envelope; a rod-like electrode insulatedly supported by the envelope and extending axially into and along substantially the entire length of the envelope; a ceramic breaker formed as an annulus to surround said electrode; said breaker being located at one end of the envelope; means for revolving the switch; means mounting the switch with its axis fixed substantially parallel to and eccentrically of the axis of revolution of said revolving means; limited quantity of mercury in said envelope; whereby said mercury upon revolution of the switch may tend to form a globular mass at any position along said envelope beyond said breaker and normally be in contact with said electrode to complete a circuit between the electrode and the envelope, and upon further revolution of the switch, said mass will flatten and withdraw from said electrode Contact; a metallic closure across the lower end of the envelope and insulated therefrom; and said electrode being fixed to said closure; and said breaker being radially spaced from said electrode to provide a mercury passage therealong.

4. A mercury tube switch for centrifugal operation comprising a sealed, tubular, metallic envelope; a rod-like electrode insulated and supported from the envelope extending axially into and substantially throughout the entire length of the envelope; means for revolving the switch; means mounting the switch with its axis fixed substantially along the envelope tending to assume a globular form suflcient in depth to contact both the envelope and the electrode; whereby upon bodily revolution of the switch may cause at a critical speed a flattening of the mercury mass to break said contact; a closure cap across the lower end of the envelope to which cap said electrode is secured; means insulating the cap from the envelope; and a ceramic annulus between the cap and the envelope and axially surrounding the electrode in spaced relation to permit passage of the mercury along the electrode through the annulus.

5. A centrifugal control comprising a rotary part; a tubular mercury switch mounted on the part to have its axis substantially parallel to the axis of revolution of said part; an electrode extending axially within the switch; and mercury in the switch limited in quantity normally to contact said electrode and to flatten at a critical speed of said part away from contact with said electrode; and a second mercury switch bodily shiftable on said part under impulse of centrifugal force between positions making and breaking an associate-d electrical circuit, said second switch being biased to one of said positions; the mercury in the first switch controlling the asmercury of the second switch controlling the circuit by change in position.

6. A centrifugal control comprising a rotary part; a mercury tube switch pivoted on the part in offset relation to the part axis to rock under the effect of centrifugal force and thereby variably position its mass of mercury relative to at least one of the electrodes of the switch; means biasing the switch toward said axis; a counterbalance member ixed in position on said part in opposing diametrical relation to the switch; said counterbalance including a xed positioned mercury tube switch axially aligned with said axis, an axial electrode therein, and a mass of mercury normally in contact with that electrode changing shape under centrifugal force to break said contact.

'7. A centrifugal control comprising a rotary part; one mercury switch mounted on the part to swing bodily under centrifugal force to control in position of the a second mercury switch mounted in fixed position on said part to have the mass of mercury therein change its shape under centrifugal force to modify control of said circuit.

8. A. centrifugal control comprising a rotary part; one mercury switch mounted on the part to swing bodily under centrifugal force to control an associated circuit by shift in position of the mercury in the switch; and a second mercury switch mounted in xed position on said part to have the mass of mercury therein change its shape under centrifugal force to modify control of said circuit; said switches being arranged in substan- JOSEPH H. STALEY. 

